I agree thateither cartridgemakes an excellent LE or self defense round but the .45 does not have a lot more energy or knock down power. The ballistics of the two arevery close.

"GUNS" June 2007 had a cover story about the Springfield XD .45 ACP. It sounds to be a very well designed and excellent overall choice. From one of the older, experienced guys at the gun store I frequent, he had good things to say about it.
I was actually looking to buy one and may eventually will for other purpose. For now I bought a handgun (Ruger Redhawk .44 Mag - 4") as a backup sidearm when we hunt Elk that borders on big bear country.
I think the Springfield XD .45 ACP is certainly worth a close look as a "carry" or personal protection sidearm though.

Does the XD have a trigger reset similar to the Glock?

But it does have more power?
Does it recoil more?

In many loadings you have to go to a "+P" loading tohave more "power"in the .45 ACP. I do not want to be on the business end of either one. Go to Winchester, Federal, and others and compare the ballistics of the two.Do a google search forDoubleTap ammo as they produce some excellent self defense ammo.

I actually find that the .40 S&W has a snappier or sharper recoil than the .45ACP. I personallyam a little more accurate with my .45ACP than I am with mytwo .40 S&W's.I don't think you can go wrong with either choice. I also don't think you would go wrong with a 9mm either.

Funny thing is, Federal's site doesn't have .45 ACP, it has .45 Auto.

Same for the Winchester site.

I think that's weird.

So, .40 S&W has higher velocities than the .45 Auto, in every comparison I did. SO I guess the .40 S&W would have more advantages.

What kind of advantage does the .45 ACP have? Is the ammo cheaper?

ACP(Automatic Colt Pistol)and Auto are the same thing. In fact on the slide of my Glock 21 it says .45 Auto. It is more of a personal choice on the two cartridges as they are so close in performance. I carrya Beretta 96(.40 S&W) daily as my duty weapon. When I am off duty, I carry a Glock 23(.40 S&W) or a Glock 21(.45 ACP). I don't feel undergunned with either pistol. Did you look at the Double Tap site? If not, look around there and you will see how close these two really are.
http://www.doubletapammo.com/php/catalog/index.php

With the .45 you can get a bigger bullet. I believe a 230 gr. where with a .40 the biggest is a 180 gr. I am just going off memory with those two numbers. And .40 S&W ammo is cheaper, and then 9mm is even cheaper.

With the .40 you can get a 200 grain bullet(Double Tap), although there are probably better choices.

I own an XD45 and I think it's a fine pistol, zero problems and no FTF issues to date. You can break this thing down and put it back together in under 20 seconds......no kidding!